Like most people, the last thing I want to think about on a sunny July weekend is where the poop goes when I flush the toilet. But if you live on Cape Cod (even seasonally) and you care about health, the environment or the cost of living and doing business on the Cape, it is in your best interest to begin to contemplate the odyssey of wastewater. Far-reaching decisions are now being made about wastewater that will impact the Cape for generations.

As most Cape Codders know, each flush delivers wastewater to the sole source Cape Cod Aquifer (CCA). The CCA is like an invisible town commons beneath our feet, like the commons that served as communal grazing areas for livestock in old New England. As with all commons, the CCA is subject to the tragedy of the commons articulated by Garrett Hardin in 1968 - a growing population will inevitably (often knowingly) destroy a commons if the use of that commons is not regulated. The CCA is a large and complex commons that everyone on the Cape uses for both water supply and wastewater disposal. The health of the CCA is also critical to the ecology of ponds, wetlands and estuaries. It’s a web of life thing.

Every year more and more toilets flush into the CCA and every year the variety of chemicals that make their way into the groundwater increases in quantity and complexity. A septic system is not a magic box that removes all the contaminants in our wastewater. Its primary purpose is to break down organic matter but relatively little chemical removal or breakdown occurs. Septic systems are 19th century technology. They work fine in rural areas where the main solution to pollution is dilution.

But in densely developed areas like Cape Cod the shortcomings of septic system technology are apparent. Ever-higher concentrations of pollutants in the CCA are the result. And with every flush, the nitrates, phosphates, cleaning products, pharmaceuticals, endocrine disruptors and the occasional pet fish eventually make their way to local ponds, brooks, estuaries and yes, water supply wells.

A recent study of Cape Cod public drinking waters by the Silent Spring Institute found 18 chemicals that you never heard of before in most of the 20 public water supply wells tested. These are so-called “emerging contaminants” that almost certainly come from septic systems. Their potential health effects? Not enough research has been done. We are the guinea pigs for future studies. And these water samples were taken from protected public sources. Those who get their water from private wells have no idea what is in their water because they don’t spend thousands of dollars a year on testing like public suppliers do. Potential contamination of private wells is the most overlooked public health threat in Massachusetts.

Septic systems release phosphates that contribute to algae blooms in ponds. Nitrogen from septic systems has been linked to ecological impacts in estuaries – the nursery of marine life. On this particular environmental issue, it’s not BP or big industry or big developments or any of “them” – it’s us.

Like many of the environmental issues that are a by-product of development and technology, the impact of wastewater on the ecology of the Cape is enormously complex and requires expertise in hydrology, chemistry, marine biology and many subsets and combinations of these disciplines. No single individual will ever fully comprehend all of the detailed ramifications of the problem.

This means that a lot of people will need to be involved in developing solutions and they will need to cooperate. This includes what are generally called “the stakeholders” – the EPA, the DEP, Barnstable County, all the towns and relevant boards, environmental groups, citizen groups and homeowners. In my humble opinion, there has not been nearly enough coordination, cooperation or communication between the stakeholders. This should be the responsibility of DEP and Barnstable County. But so far communication has generally been one-sided and there seems to be way too much emphasis on getting things done quickly rather than getting things done openly and effectively. Public comment and review of the MEP studies (the basis for most of the coming wastewater plans) is discouraged. In fact, despite the best efforts of towns and their technical consultants, some of the key data and analyses behind the MEP studies are unavailable for review by anyone. This is not transparency in government and it is bound to complicate matters when towns are asked to vote to appropriate difficult-to-imagine sums of money.

There is not enough money in the world to completely understand all of the potential impacts of human development on the ecosystem and devise the perfect and most cost-effective solution. This is the real world. We can only do the best we can with the resources we have. Sometimes that means assuming worse case scenarios or making crude estimates and rounding off numbers. But even if few of us can fully understand the science and technology behind these potential solutions, all of the data and analyses that lead to potentially costly solutions need to be open and available for public review. We may need to learn a new kind of toilet training, but we are not children.

Jesse Schwalbaum is a hydrogeologist with extensive experience on Cape Cod. He is the author of Understanding Groundwater.